Means for controlling the exhaust recirculation

ABSTRACT

In internal combustion engines, a means for controlling exhaust recirculation in such a manner as to increase and decrease the rate of recirculation as the load on the engine decreases and increases respectively while the engine is running continuously at high or normal speed, and to cut off the recirculation under conditions of acceleration, engine braking, and low revolution slower than a predetermined speed.

Naito et al.

United States Patent 1191 MEANS FOR CONTROLLING THE EXHAUST RECIRCULATION Inventors:

Assignee:

Filed:

Appl. No.:

Noriho Naito, Kariya; Yutaka Kawashima, Okazaki; Akira Masuda, Kariya, all of Japan Nippondenso Co., Ltd., Kariya, Japan July 27, 1973 Foreign Application Priority Data Aug. 31, 1972 Japan 47-87278 us. on 12'3/119 A 1111. (:1. F02M 25/06 Field of Search name A References Cited UNITED STATES PATENTS McKinley 123/119 A Nov. 4, 1975 3,507,260 4/1970 Walker 123/119 A 3,605,709 9/1971 Nakajima et a1 123/119 A 3,610,219 10/1971 Sciabica 123/119 A 3,675,633 7/1972 Nakajima et a1... 123/119 A 3,678,909 7/1972 Barker et al. 123/119 A Primary Examiner-Charles J. Myhre Assistant Examiner-Sheldon Richter Attorney, Agent, or Firm-Cushman, Darby & Cushman [57] ABSTRACT In internal combustion engines, a means for controlling exhaust recirculation in such a manner as to increase and decrease the rate of recirculation as the load on the engine decreases and increases respectively while the engine is running continuously at high or normal speed, and to cut off the recirculation under conditions of acceleration, engine braking, and low revolution slower than a predetermined speed.

6 Claims, 3 Drawing Figures 'UIOONWOHWOUW US. Patent Nov. 4, 1975 Sheet 1 of 2 3,916,857

I US. Patent Nov.4, 1975 Sheet20f2 3,916,857

F l G. 2

[U g w LOAD LOAD 5 LOAD 2 I X LU 6 LOAD U) U) LU Z X 2 I FLOW RATE OF RECIRCULATING GASES ANGLE OF CONTROL 0 VALVE LEVER 9 ANGLE OF ACCELERATOR LEVER 9 MEANS FOR CONTROLLING THE EXHAUST RECIRCULATION This invention relates to an exhaust recirculation systems for internal combustion engines and more particularly to a means forcontrolling the recirculation of exhaust gases in such systems.

It is known that in internal combustion engines, especially in vehicle engines, the density of NOx in emission gases can be greatly reduced by having the exhaust gases return to suction side of the engine for recirculation, and this feature is quite appreciable for antipollution.

However, the exhaust recirculation brings about, on the other hand, some disadvantages such as reduction in engine horse power, elevated CO and HC densities, and thickened exhaust smoke especially in diesel engines.

These disadvantages in turn presents some problems, which prevents the adoption of exhaust recirculation system.

In general, NOx is mainly produced at high tempera ture of combustion chamber, which follows continuous runnings at normal or high speed of the engine, and it is particularly effective to have the exhaust gas return to air inlet for recirculation so as to minimize the NOx density.

However, at the same time, the thickness of the smoke, which tends to increase as the engine load increases, will be enhanced to an unallowable extent if the recirculation is uncontrolled for varying engine load at continuous running.

When the engine is running at low speed or when the engine is idling, the NOx density is much lesser since the combustion chamber is not so heated, while CO and BC densities, as well as smoke thickness are relatively high.

Therefore, it is not only useless but also harmful to effect the recirculation when the engine is idling or at low speed, since the CO and I-IC densities and smoke thickness are further increased.

It is also unfavourable to effect the recirculation while the engine is being accelerated, since this phase is also innocent of NOx, and since the reduction in engine horse power powing to recirculation obstructs the desired acceleration of the vehicle.

It should also be pointed out that the recirculation should not be effected when the engine brake is used, since I-IC and CO densities are relatively high, while NOx is negligibly small, under such condition.

In case of vehicles as have been provided with exhaust brakes, the recirculation of exhaust gases under this phase results in spoiling the braking effect of the exhaust brake.

Therefore, it is an object of the present invention to enable to minimize the emission of NOx without being accompanied by unfavourable incrassation of CO and HC densities and smoke thickness, and by reduction in accelerating power.

According to invention, there is provided a means for controlling the recirculation of exhaust gases comprising, a control valve provided at intermediate of the recirculation passage, an interlocking means adapted for decreasing the opening degree of said control valve when acceleration lever is moved towards the maximum power position and increasing said opening degree when the acceleration lever is moved towards the minimum power position, and a means for closing said control valve freely from said interlocking means upon detecting that the engine is under one of conditions of acceleration, engine braking, and low revolutions slower than a predetermined value.

In a preferred embodiment, the interlocking means comprises a cam operable by acceleration lever, and a connecting link mechanism having at one end a cam follower for engagement with said cam and linked to the control valve at the other end.

The means for closing control valve may comprise an electro-magnetical means adapted for closing said control valve when energized, a first detecting means for allowing energization of said electro-magnetical means upon detecting an abrupt movement of accelerator lever for accelerating engine, a second detecting means for allowing said energization upon detecting that the acceleration upon detecting that the acceleration lever is at almost released position, a third detecting means for allowing said energization upon detecting that the engine revolution is slower than a predetermined value.

These and other objects and features of the invention will be described hereinafter referring to a practical embodiment as illustrated in the attached Figures in which;

FIG. 1 is a schematic view of a means for controlling exhaust recirculation according to invention.

FIG. 2 is a graph showing the relationship between the thickness of the exhaust smoke and the rate of the recirculating exhaust gases.

FIG. 3 is a graph showing a desirable relationship between angle of accelerating lever and angle of control valve lever.

Referring to FIG. 1, a control valve 2 is provided at intermediate of the recirculation passage 4 which is connecting the exhaust side to the suction side of the engine, to control the flow rate of the recirculating gases.

The opening degree of said control valve 2 is adapted to be changed by the motion of acceleration lever 8 through the medium of a cam 5 linked to said acceleration lever 8, and ofa control valve lever 3 linked to the control valve 2 at one end with a cam follower at the other end for engagement with said cam 5.

The interlocking means as written above operates so as to decrease the opening degree of the control valve 2 when the acceleration lever 8 is moved towards the maximum power position, and to increase said opening degree when said lever 8 is moved toward the minimum power position.

Namely, the angles 6 and 6 as illustrated in FIG. 1 varies have therebetween a relationship as shown in FIG. 3.

The control valve 2 is closed independent of the angle 6 of the accelerating lever 8, upon energizing of the electro-magnetic coil 12 which is adapted to be energized on closing of any one switch of first switch 6, the second switch 9, and the third switch (not shown) which is controlled by a computor 11. One such suitable computer is described in Japanese utility model publication 18/75/71 published June 25, 1971, and entitled Compressor Controlling Device."

The first switch 6 is closed by an abrupt movement of the accelerating lever 8 towards the maximum power position through the medium of a conventional dashpot 7 which does not transfer a gradual movement of the accelerating lever 8.

The second switch 9 is a conventional micro limit switch which is closed by accelerating lever 8 when said lever 8 is at almost the minimum power position.

Also a computor l1 permits energization of electromagnetic coil 12 by closing the third switch when the engine is slower than a predetermined speed, on receipt of electric signals from a revolution detecting electromagnetic pickup 10.

In operation, the control valve 2 is kept opening to permit the recirculation of exhaust gases while the engine is continuously running at normal or at high speed, so that the density of NOx is greatly reduced.

It should be noted, under such conditions that the thickness of exhaust smoke which tends to get higher, as seen from FIG. 2, as the engine load as well as the flow rate of recirculating gases increases, cannot exceed the predetermined value, since when the acceleration lever 8 is moved towards the maximum power position the interlocking means acts to decrease the opening degree of the control valve 2 so as to reduce the flow rate of the recirculating gases.

Thus the reduction of NOx densities is effected without incrassation of exhaust smoke thickness, while the engine is running continuously at high or at normal speed.

When the acceleration lever 8 is moved abruptly towards its maximum power position for acceleration, such abrupt movement is transferred to switch 6 through the medium of dash-pot 7, so as to close said first switch 6 to close said control valve 2, whereby the recirculation of the exhaust gases is cut off to prevent unfavourable decrease in accelerating power and incrassation of CO and HC densities and of exhaust smoke thickness.

When the engine brake is used and when the engine load is small, the acceleration lever is at almost the are closed.

It will also be obvious that the computor and the electromagnetic pickup in the embodiment may be substituted by a conventional mechanical switches as equipped with fly weights to produce any centrifugal force in accordance with the revolution.

minimum power position and pushes the limit switch 9,

so as to close the control valve 2 by energizing the electro-rnagnetic coil 12, whereby the recirculation is stopped to prevent the elevation of CO and HC densities and exhaust smoke thickness.

When the engine is idling or running at slower speed than predetermined speed, the computor ll acts to cut off the recirculation so that the exhaust smoke thickness does never get higher.

It should be appreciated that the means for controlling the exhaust recirculation of the present invention enables it to minimize the emission of NOx without being accompanied by incrassation of HC and NO densities and exhaust smoke thickness and by unfavourable decrease of accelerating power, by adopting the exhaust recirculation system.

Although one specific embodiment have been described it will be obvious to those skilled in the art that vbarious modifications may be made.

For example, the means for closing control valve may comprise a diaphragm adapted for closing said control valve when the suction vacuum of the engine is applied thereto, and a electro-magnetic valve for permitting said application of suction vacuum when the switches Further changes may be made without departing from the spirit of the invention which is intended to be limited solely by the appended claims.

What is claimed is:

1. A device for controlling an exhaust gase recirculation system in an internal combustion engine having a recirculation passage communicating an exhaust side of the engine and a suction side for recirculation of exhaust gases comprising:

.a recirculation control valve mounted in said passage for varying the flow rate of recirculating gases,

an acceleration lever having a position which determines engine power,

interlocking means connecting said acceleration lever and control valve so that the flow rate is varied as a function of the lever position including cam means coupled to said lever and valve for decreasing the opening of said valve and the flow rate when said lever is moved toward the maximum power position and increasing the opening of said valve and the flow rate when said lever is moved toward the minimum power position,

means for detection engine speed and producing an actuating signal whenever the detected speed is less than a predetermined value, means for detecting the rate of movement of said lever and producing an actuating signal whenever the detected rate exceeds a predetermined value,

means for detecting the minimum power position of said lever and producing an actuating signal whenever said minimum power position is detected, and

control means connected to each of said detecting and producing means for closing said valve to substantially prevent flow of recirculating gases whenever an actuating signal is produced.

2. A device as in claim 1, wherein said control means includes an electromagnetic coil having portion connected to said valve for closing said valve when said actuating signal is produced.

3. A device as in claim 1, wherein said engine is a deisal engine.

4. A device as in claim 1, wherein said minimum power position detecting and producing means includes a switch.

5. A device as in claim 4, wherein said rate of movement detecting and producing means includes a dashpot connecting said lever to one of said switches so as to actuate said one switch when said rate exceeds said predetermined value.

6. A device as in claim 1, wherein said engine braking detecting and producing means includes a switch positioned to be actuated when said lever is in the minimum power position. 

1. A device for controlling an exhaust gase recirculation system in an internal combustion engine having a recirculation passage communicating an exhaust side of the engine and a suction side for recirculation of exhaust gases comprising: a recirculation control valve mounted in said passage for varying the flow rate of recirculating gases, an acceleration lever having a position which determines engine power, interlocking means connecting said acceleration lever and control valve so that the flow rate is varied as a function of the lever position including cam means coupled to said lever and valve for decreasing the opening of said valve and the flow rate when said lever is moved toward the maximum power position and increasing the opening of said valve and the flow rate when said lever is moved toward the minimum power position, means for detection engine speed and producing an actuating signal whenever the detected speed is less than a predetermined value, means for detecting the rate of movement of said lever and producing an actuating signal whenever the detected rate exceeds a predetermined value, means for detecting the minimum power position of said lever and producing an actuating signal whenever said minimum power position is detected, and control means connected to each of said detecting and producing means for closing said valve to substantially prevent flow of recirculating gases whenever an actuating signal is produced.
 2. A device as in claim 1, wherein said control means includes an electromagnetic coil having portion connected to said valve for closing said valve when said actuating signal is produced.
 3. A device as in claim 1, wherein said engine is a deisal engine.
 4. A device as in claim 1, wherein said minimum power position detecting and producing means includes a switch.
 5. A device as in claim 4, wherein said rate of movement detecting and producing means includes a dash-pot connecting said lever to one of said switches so as to actuate said one switch when said rate exceeds said predetermined value.
 6. A device as in claim 1, wherein said engine braking detecting and producing means includes a switch positioned to be actuated when said lever is in the minimum power position. 